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Carrying Value BBB+, BBB, BBB- Standard & Poor's, BBB Plus, BBB, BBB Minus Rating [Member] Standard & Poor's, BBB Plus, BBB, BBB Minus Rating Assets Assets, Fair Value Disclosure [Abstract] Due in one year or less Debt Securities, Available-for-Sale, Fair Value, Maturity, Allocated and Single Maturity Date, Year One Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward] Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward] Variable rate percentage (in percent) Debt Instrument, Basis Spread on Variable Rate South Carolina SOUTH CAROLINA Sales and marketing Selling and Marketing Expense [Member] Weighted-average common shares outstanding: diluted (both Class A and B) (in shares) Weighted Average Number of Shares Outstanding, Diluted Short-term investments Debt Securities Available For Sale Current [Member] Debt Securities Available For Sale Current Net realized gains on investments Debt Securities, Available-for-Sale, Realized Gain (Loss) Operating expenses: Operating Expenses [Abstract] Realized losses on investments Debt Securities, Available-for-Sale, Realized Loss Purchases of fixed assets Payments to Acquire Property, Plant, and Equipment Additional Paid-in Capital Additional Paid-in Capital [Member] Total assets Assets Revision of Prior Period [Axis] Revision of Prior Period [Axis] Cover [Abstract] Direct Direct Premiums Earned Premiums receivable, net of allowance of $2.7 and $2.8 at September 30, 2023 and December 31, 2022, respectively Premiums Receivable, Net Common stock—share-based compensation expense APIC, Share-Based Payment Arrangement, Increase for Cost Recognition Ceded Ceded Premiums Earned Restructuring and Related Activities [Abstract] Schedule of Comprehensive Loss For Reinsurance Schedule of Direct and Assumed Premiums Written Effects of Reinsurance [Table Text Block] Vested (in dollars per share) Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Vested in Period, Weighted Average Grant Date Fair Value Forfeited, expired or canceled (in shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Forfeitures and Expirations in Period Total operating expenses Total operating expenses Operating Expenses Reinsurance recoverable and receivable, net of allowance of $2.9 and $0.2 at September 30, 2023 and December 31, 2022, respectively Reinsurance Recoverable for Paid and Unpaid Claims and Claims Adjustments Schedule of Error Corrections and Prior Period Adjustment Restatement [Table] Schedule of Error Corrections and Prior Period Adjustment Restatement [Table] Net (decrease) increase in cash, cash equivalents and restricted cash Cash, Cash Equivalents, Restricted Cash, and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect Cash flows from financing activities: Net Cash Provided by (Used in) Financing Activities [Abstract] Short Term Warrant Short Term Warrant [Member] Short Term Warrant Secured debt Secured Debt [Member] Realized gain value Gross Investment Income, Operating Equity Component [Domain] Equity Component [Domain] Incurred expense for commutations of certain reinsurance agreements Liability for Unpaid Claims and Claims Adjustment Expense, Exchange Of Reinsurance Agreements Liability for Unpaid Claims and Claims Adjustment Expense, Exchange Of Reinsurance Agreements Debt Instrument [Line Items] Debt Instrument [Line Items] Weighted-average common shares outstanding: basic (both Class A and B) (in shares) Weighted Average Number of Shares Outstanding, Basic Entity Current Reporting Status Entity Current Reporting Status Concentration Risk Type [Domain] Concentration Risk Type [Domain] Interest on bonds Bonds [Member] Operating loss Operating loss Operating Income (Loss) Net realized gains on investments Realized Investment Gains (Losses) Redeemable convertible preferred stock (as converted to common stock) Nonvested Shares Subject To Repurchase [Member] Nonvested Shares Subject To Repurchase Concentration Risk Benchmark [Axis] Concentration Risk Benchmark [Axis] Revenues: Revenues [Abstract] Beginning balance Ending balance Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Aggregate Intrinsic Value, Nonvested Interest on deposits and cash equivalents Cash and Cash Equivalents [Member] Statement [Line Items] Statement [Line Items] Estimated Fair Value Estimate of Fair Value Measurement [Member] Reinsurance premiums payable Reinsurance premiums payable Increase (Decrease) in Reinsurance Payables Schedule of AFS Debt Securities Debt Securities, Available-for-Sale [Table Text Block] Loss and loss adjustment expense reserves Liability For Claims And Claims Adjustment Expense, Gross Liability For Claims And Claims Adjustment Expense, Gross Nonvested shares subject to repurchase Redeemable Convertible Preferred Stock [Member] Type of Restructuring [Domain] Type of Restructuring [Domain] Tranche 1 Share-Based Payment Arrangement, Tranche One [Member]